Can this happen randomly? I had my heads/cam/intake installed in May, and I have always thought that it might not be runnign up to par, but especially as of late. I was going over the engine a little bit cleaning it.. and noticed the throttle cable had some slack in it. I had someone go step on the gas while I wantched it.. and floored it was maybe 80% open! I adjusted the cable coming off the cruise control to the throttle body and tightened it back up so it opens 100% now.. can this cable slip and cause this? Or is it more likely that it was NEVER tight since the re-install of parts?

 

I dont know, but I'll be sure to check that tomorrow.

 

bump. I'd really like to know if anyone has an answer.

 

Hello, I just bought my 02 Z28, its 90k miles and 100% stock. I just cleaned my MAF and decided to check if I was getting WOT. Had my girl go and mash the gas and I too, was getting about 80% throttle it seemed. I adjusted the same cable, from cruise to TB, and its getting WOT now...

So I wonder if its like that from the get go? Now I am worried about doing the bump stop mod, and getting more than WOT, can the throttle blade go past WOT, and actually have the throttle blade go too far, and actually be like 90% throttle, but from bending back too far?

The last paragraph is kinda screwy, but if you have a good imagination, you will see what I am talking about!

 

Yes, you can go too far on the bump stop mod. If I recall it's like 4.72 max using a voltage meter. And as far as slack, that is very common and why the adjustment is available to us. If you have TCS you can take off the cover to it (located right by the battery) and turn it till it stops; it should open the TB without having to have someone in the car pushing the go pedal down.

 

when i installed my tb i had that problem. i knew the car wasnt drivin to its potenital. it was only opening to like 80% like u guys. so i adjusted it and know its drivin good. but for ur situation, i think it isnt possible for it to slip. probably happened when u installed the intake, their was slack left in the cable.

 

So it may or may not have been the builder's fault.. since someone with a stock car had this problem.. but it is definate that the throttle position was NOT checked after my upper engine package install.. since it doesn't slip.

Answers some of my questions

Thanks guys

 

You want to re-snug the adjustable cables any time you change
stuff, and rechecking once in a while is not a bad idea. There is
also a variable amount of slack in non-adjustable cable runs that
can want more effort to take up (spacers or bending the pedal
arm).

 

Hmm... Wonder if this could possibly be my problem? Need to check this. So if you have slack, will the TPS never read 100% throttle position, or is the TPS not calibrated (IOW, pedal to floor is 100% TP when throttle is only 80%).

 

pedal to floor is 100% TP when throttle is only 80%

 

thanks.

 

This would mean that TP sensor is telling the computer the wrong TP; therefore, the computer is looking up the wrong values for fuel and spark.

 

are you sure? if throttle position is only 80% with the pedal 100% floored, wouldn't the CPU still only see 80%? Isn't it going to read off the metered air through the MAF for fuel?

 

It will read air flow off of MAF, but isn't throttle position used in PE? I know in old speed density tuning (no MAF), that TP is used to trigger power enrichment during acceleration.

 

You can twist the cable 1/2 turn at a time till the slack is to you're liking.
Swing it out of the TB and twist. You'll be surprised. I did it when I ground my bump stop cause my cable didn't even pull to the stop. Idle adjusted itself.

 

No, the computer does not evaluate the pedal, it evaluates the tps %. If you have the pedal all the way down and your tps is only reading 80%, then the values will be for 80% throttle.

 

Hmmmm when I hit the pedal it seems like there is a dealy to the rev, maybe I will have to look into this.

 

I have the same problem and need to fix mine. I recently started using EFI Live and it says it's only opening 92% when it's on the floor. It may have been this way for years for all I know.